Recommend selective sync. Of course it will be available bit by bit if at all . A first "bare bones" shot could be as simple as include or exclude all subfolders, with exclude as default. Provide override option to include all subfolders having inherited folder properties, and to customize inclusion of specific excluded folders (even if done by manual selection). This simple first shot could get the ball rolling with more complex features likely to follow! Given the fine but complex desires on this feature will likely be an impediment both for the developers and added complexity for the general user. Less is More at this juncture.